The present invention relates to a system for preparing elastic yarns so that they may be batch or package-dyed by methods heretofore typically useful only for dyeing inelastic yarns. More particularly, the present invention relates to an apparatus and method for tensionless winding of low modulus high elasticity yarns into a low density, uniform, wound cylindrical package, and that inventive package itself.
It has been customary in the textile industry to dye or otherwise impart color to yarns by the batch process commonly known as package dyeing. In that process, an entire package, i.e. cone or bobbin of yarn, is batch dyed simultaneously. That package dyeing process was a substantial improvement over other forms of dyeing, and that process has now been used for many years in the textile industry.
However, there remain considerable difficulties in the dyeing of elastic yarns since such yarns typically have no uniform nominal shape, and even very slight tensions can result in substantial deformation of such yarns. If such yarns are wound into packages in the same manner as more inelastic yarns are packaged, the deformation, i.e. extension, which normally occurs, makes such wound packages very tight, dense structures. Such yarn package structures are unsuitable for batch or package dyeing because their density and lack of porosity prevents total penetration of the dyeing medium, and thus results in non-uniform coloration and non-uniform yarn properties after batch or package dyeing.
In the typical yarn winding processes, a perforated cylinder or spring core was rotated about its axis either by direct power to the axis of rotation, or by circumferential contact with another rotating member such as a steel roll. Thus, the yarn was pulled onto the desired cylinder necessarily creating tension in the yarn and extension of the yarn during winding. Such tension and extension are of negligible consequence when winding relatively rigid, inelastic yarns, since the initial modulus of elasticity of such yarns is quite high and the subsequent elongation is so low that it has no serious consequences in the wound package. However, such techniques are not suitable for highly elastic, low modulus yarns because only minor amounts of tension result in very substantial amounts of extension during winding, thus resulting in non-uniformities in the yarn condition as wound in the package, in addition to the yarn package densities which are unsuitable for package dyeing.
As previously indicated, in package dyeing yarn packages are treated with yarn colorants according to standard practices which typically involves passing a liquid medium through the wound package radially in both directions. Such radial injection of liquid colorant into the package is successful only if the package is of sufficiently low density to permit flow of the colorant medium throughout the package, i.e. the colorant medium is able to seek all available paths to contact every portion of every yarn in the package. Thus it is again noted that successful package dyeing makes it quite desirable that the package being dyed be of a density and porosity such that the liquid dyeing medium may easily and efficiently permeate the entire package structure. This goal has historically been substantially impaired where attempts were made to package dye tightly wound packages of low modulus high elasticity yarns.
Other previous attempts have been made to make more porous, less dense, packages of low modulus highly elastic yarns. One such attempt was to wind the yarns on a much larger diameter core and then to allow the core to relax to a size comparable to the core of a normal package. This was commonly done on a collapsible bobbin. Another method was disclosed in Claiborne et al U.S. Pat. No. 3,281,087. Still another method is to use normal winding techniques, but to attempt to supply the yarn loosely to the package being formed by the use of over-feed rolls, thereby reducing the amount of extension and deformation of the yarn. However, in the case of direct winding, there is no way to distribute the yarn uniformly throughout the package without the usual traversing mechanisms which supply the yarn onto a revolving bobbin in a generally spiral pattern. However, the traversing mechanisms which deliver the yarn uniformly into such packages necessarily add tension to the yarn. Thus such prior methods have still not produced satisfactory porous, low density packages of low modulus high elasticity yarns.